1. Technical Field
This disclosure generally relates to electronics, and, in particular, to generating a reference current for a memory device.
2. Description of the Related Technology
Phase change memory (PCM) is a form of non-volatile memory made from a phase-change material. An example of a phase-change material is Germanium-Antimony-Tellurium (GST). When a cell of GST material is heated beyond its melting point and cools relatively rapidly, the phase-change material of the cell is in an amorphous state and can have a resistance associated with a first state, such as logic 0. When the cell of GST material is heated and is cooled relatively slowly, the phase-change material of the cell is in a crystalline state and can have a resistance associated with a second state, such as logic 1. The cell of GST material can also be heated to a relatively lower temperature, such as a temperature associated with crystallization to achieve the crystalline state. Intermediate states are also possible for multi-level cells having more than two states.
Non-volatile memories, such as PCMs, can determine a value of a data digit, such as a bit, stored in a non-volatile memory cell by comparing an indication of current associated with the non-volatile memory cell with an indication of a reference current. A read current can be indicative of a resistance associated with a particular state of a PCM cell. To determine a value of the data digit stored in a PCM cell, a sense amplifier can compare an indication of read current associated with a binary PCM cell with an indication of a reference current to determine whether the PCM cell stores a logic 0 or a logic 1 value.
In a PCM array, there can be a distribution of read currents for detecting each state of a PCM cell. For example, for an array of binary PCM cells, there can be a distribution of read currents for reading logic 0 and another distribution of read currents for reading logic 1 from PCM cells of the array. Accordingly, it can be desirable to have as large of a read margin as possible. A read margin can be the mean distance between the tails of the read current distributions for different states of a PCM cell. Variations in read current relative to the reference current can undesirably reduce read margin. Such a reduction in read margin can, in some instances, result in read errors when incorrect values are determined for particular memory cells.
Accordingly, a need exists for improved generation of a reference current in a non-volatile memory device.
To avoid repetition of description, components having the same or similar function may be referenced by the same reference number.